Saw-tooth wave generator



Dec. 5, R ANDRlEU SAW-TOOTH WAVE GENERATOR Filed March 17, 1937 AAAAAAA-mmm mm l INVENTOR ROBERT ANDRIEU ATTORNEY Patented Dec. 5, i939 UNE'E'EESTATES FAHENT @FFECE SAW-TOOTH WAVE GENERATOR tion of GermanyApplication March 17,

1937, Serial No. 131,322

In Germany March 19, 1936 a Claims.

My invention relates broadly to apparatus for the generation of acurrent or voltage of serrated or so-called saw-tooth wave formation,and more particularly to an apparatus which is controllable by impressedsynchronizing impulses which themselves are segregated by the apparatusin order to be actuated by the correct impulse.

My previous application United States appiication Serial No. 51,499,filed January 30, 1936, describes a circuit arrangement for producing acurrent of saw-tooth form in the deflecting coil of a cathode ray tube,and preferably a tube used for television purposes. Ther are providedparallel to the deflecting coil or coils two different currentconducting branches or circuits, of which one contains a multi-grid tubeand a potential source and the other a diode and likewise a potentialsource. The potential source which is connected in series with the diodeis impressed with a smaller potential than the potential source in thecurrent branch containing the multigrid tube. It was assumed in thearrangement according to the parent application that blocking impulseswere periodically impressed on one of the control grids oi the multigridtube resulting thus in a current course in deflecting coil of saw-toothcharacter. Representative impulses of such type are the signal impulseswhich are filtered out in a television receiver after demodulation oithe carrier wave modulated with such impulses and the image pattern.

The invention concerns a further development of the circuit arrangementdisclosed in the parent application and has for its purpose to utilizethe saw-tooth generator not only for the line deflection but at the sametime for separating the vertical impulses from the signal impulses, saidvertical impulses difiering in their duration with equal amplitude fromthe line impulses in the manner usual in television. This isaccomplished in accordance with the invention in that in the circuit ofa screen grid of the multigrid tube is provided an RC-member to which iscoupled an amplitude selection stage.

My invention will be best understood by referring to the accompanyingdrawing, in which Fig. 1 illustrates an embodiment of the invention,

Figs. 2 and 3 are explanatory curves.

Referring to Fig. l, a multigrid tube ii), which is shown as usualscreen grid tube for the sake of simplicity, has joined serially to itsanode and in the anode-cathode circuit, a deflecting coil ll of a Brauntube. A diode l2, and I4 2. resistance-capacity circuit whose timeconstant must be chosen very great in comparison to the line duration,and as a rule even great with respect to the image duration areconnected serially and the combination is connected in shunt to the coilH. A potential source It energizes the plate of the tube H). In thescreen grid circuit of tube H3 and connected in series in the screengrid-cathode circuit is disposed a resistance tion of current in thedeflecting coil 5 I, with the result that the current direction in thedeflecting coil has after completion of this free half-oscillation theopposite direction and practically the same amount as at the start ofsame. For the separation, to be explained in what follows, of thevertical impulses from the line impulses, it must merely be kept in mindthat current flows through the screen-grid circuit of tube Ill duringthe line duration D in Fig. 1, but that on the other hand the screengrid circuit is without current during the line pause ZP, as Well asduring vertical pause VP (see Figs. 1, 2 and 3). This current course inthe screen grid circuit is shown in Fig. 2. If current now flows in thescreen grid circuit, condenser it will take on a charge in the sense ofthe indicated plus and minus signs resulting at the same time in a shiftof potential at point A in negative direction. This is illustrated inFig. 3 which shows the potential variations of the point A of Fig. 1.

But during the line pause, condenser l6 discharges through resistancel'! to a degree which is dependent upon the time constant of theresistance-capacity circuit it] so that the potential at point A (seeFig. 1) must move at the same time in a positive direction. In thismanner the potential variations occur at point A as shown in Fig. 3during the continuous arrival of line impulses. But if during a verticalpause the tube ill is without current for a longer period, condenser I6discharges completely through resistance H, or at least to a much higherdegree than during the short line pauses. During this time, potential Awanders as in the case of the short line pauses in positive direction.If during this time for instance value -6 is exceeded, the saw-toothgenerator may be started for the vertical deflection by means of anamplitude selection stage on which is impressed the potential at point Aand which may for instance consist of a correspondingly biased amplifiertube For given cases the arrangement may also be designed in the mannerthat the input tube, or the sole tube of the saw-tooth generator, iscontrolled directly by the potential at point A for the verticaldeflection. After completion of vertical pause VP the potential courseof the resistance capacity circuit I5 again assumes the course shown tothe left of Fig. 3 within a few lines.

What I claim is:

1. A saw-tooth wave generator comprising a multigrid vacuum tubecontaining anode, cathode and a plurality of grids, an inductive memberserially joined to said anode and connected in the anode-cathode circuitof said tube, a circuit connected in parallel with said inductive membercomprising a unidirectional conductor and a circuit of predeterminedtime constants, an electrical circuit comprising a parallel joinedresistance and capacity serially joined to one of the grids of said tubeand connected in the grid-cathode circuit of said tube and an inputcircuit connected between the other grid of the plurality of grids andthe cathode.

2. A saw-tooth wave generator comprising a multigrid vacuum tubecontaining anode, cathode and a plurality of grids, a deflecting coilserially joined to said anode and connected in the anode-cathode circuitof said tube, a circuit connected in parallel with said inductive membercomprising a unidirectional conductor and a circuit of predeterminedtime constants, an electrical circuit comprising a parallel joinedresistance and capacity serially joined to one of the grids of said tubeand connected in the grid-cathode path of said tube and an input circuitconnected between the other grid of the plurality of grids and thecathode.

3. A saw-tooth wave generator comprising a multigrid vacuum tubecontaining anode, cathode and a plurality of rids, an inductive memberserially joined to said anode, a circuit connected in parallel with saidinductive member comprising a unidirectional conductor and acir.- cuitof predetermined time constants, an electrical circuit comprising aparallel joined resistance and capacity serially joined to one of thegrids of said tube and connected in the gridcathode path of said tube,and means for impressing electrical signals onto a control electrodecomprising another of the grids of said tube.

4. A saw-tooth wave generator comprising a multigrid vacuum tubecontaining anode, cathode and a plurality of grids, a deflecting coilserially joined to said anode and connected in the anodecathode path ofsaid tube, a circuit connected in parallel with said inductive membercomprising a unidirectional conductor and a circuit of predeterminedtime constants, an electrical circuit comprising a parallel joinedresistance and capacity serially joined to one of the grids of said tubeand connected in the grid-cathode path of said tube, and means forimpressing electrical signals onto a control electrode comprisinganother of the grids of said tube.

ROBERT ANDRIEU.

